Magnetic storage systems using rigid magnetic storage disks rotatable about a central axis have been known and used in the past. Also, magnetic strips have been used on credit card-sized memory devices for storing data and for reading the data when such a device is passed through a machine capable of reading data from and writing data onto the magnetic strip of the card. For the most part, read/write machines have certain drawbacks, one of which is lack of simplicity and proper registration of the card with respect to the magnetic head that reads data from the card or writes data onto the card. Because of these drawbacks, a need has arisen for an improved system for storing data on a magnetic medium having the size of a conventional credit card to allow the credit card to be carried from place to place and be quite versatile in use with a data storage and read out machine. The present invention satisfies this need by providing apparatus and method for reading data from and writing data onto the magnetic storage medium of such a card.